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Ofdm-modulated-wave output unit and distortion compensating method

Inactive Publication Date: 2009-12-17
NEC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0015]It is an object of the present invention to provide an OFDM-modulated-wave output unit and a distortion compensating method which are capable of compensating in a short delay time a distortion generated when the OFDM-modulated wave has a peak.

Problems solved by technology

If such an OFDM signal is input to a power amplifier having a non-linear characteristic, there occurs degradation of characteristics such as degradation of transmission characteristic and increase in the out-of-band radiation.

Method used

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  • Ofdm-modulated-wave output unit and distortion compensating method
  • Ofdm-modulated-wave output unit and distortion compensating method
  • Ofdm-modulated-wave output unit and distortion compensating method

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Embodiment Construction

[0023]Hereafter, an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows the configuration of an OFDM-modulated-wave output unit according to the embodiment of the present invention. The OFDM-modulated-wave output unit 100 includes a serial / parallel conversion circuit (S-P conversion circuit) 101, IFFT circuits (inverse-fast-Fourier transform circuits) 102 and 105, a GI (guard interval) addition circuits 103 and 106, weighting D / A converters 104 and 107, a orthogonal modulation circuit 112, a power amplifier 113, an amplitude extraction circuit 108, a GI-counterpart addition circuit 109, a continued-peak control circuit 110, a weighting D / A (digital / analog) converter 111, a power-amplifier control circuit 114, a power-amplifier-characteristic compensation data table 115, and a compensation-value-selection control circuit 116.

[0024]The S-P conversion circuit 101 converts an input serial-data string into pa...

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Abstract

OFDM (orthogonal frequency division multiplex)-modulated wave output unit. An amplitude extraction section (108) extracts amplitude of an OFDM-modulated wave. A power-amplifier control section (114) sets the power supply of a power amplifier (113) to exceed the rated power when the extracted amplitude exceeds a specific amplitude, to expand the saturation point of the power amplifier. A compensation-value-selection control section (116) compensates the nonlinear characteristic of the power amplifier, when the power-amplifier control section expands the saturation point of the power amplifier.

Description

FIELD OF THE INVENTION[0001]The present invention relates to an OFDM-modulated-wave output unit and a distortion compensating method and, more particularly, to an OFDM-modulated-wave output unit that generates an OFDM-modulated wave and a distortion compensating method used in such an OFDM-modulated-wave output unit.BACKGROUND OF THE INVENTION[0002]In an OFDM (orthogonal frequency division multiplex) technique, the frequency spectrum of the signal used therein is close to a rectangle, whereby a higher utilization efficiency of the frequency is obtained. In addition, the OFDM technique has a significant resistance against a delayed wave because the symbol length can be made larger than the single carrier, and addition of a guard interval, if employed, renders the OFDM technique stronger in a multi-path environment. On the other hand, in the OFDM technique, which performs multi-carrier transmission wherein a larger number of subcarriers exist, the OFDM signal has a larger peak power i...

Claims

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Application Information

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IPC IPC(8): H04L25/03
CPCH03F1/0211H03F1/3241H04B1/0475H04L27/366H04B2001/0441H04L27/2626H04L27/361H04B1/0483H03F1/3223H03F3/24H04B1/62H04L27/2627
Inventor FUJIMOTO, YOSHINORI
Owner NEC CORP